Battery Electric Vehicles (BEV), Extended Range Electric Vehicles (EREV), and Hybrid Electric Vehicles (HEV) can be powered in at least one electric-only propulsion mode, i.e., an electric vehicle (EV) mode. One or more high-voltage traction motors provide motor torque sufficient for powering the vehicle in such a mode. Each traction motor is energized via battery power supplied by a high-voltage energy storage system (ESS). The ESS can be recharged as needed during vehicle operation, such as during regenerative braking. The ESS may also be recharged when the vehicle is not running by connecting the ESS to an offboard power supply. When a state of charge of the ESS is largely depleted in an EREV, a small internal combustion engine can be automatically started and used to power an electric generator. The power output from the generator provides the required electrical energy for sustaining the EV mode.
Vehicle powertrains include a transmission that transfers motor torque from a driven member of the traction motor to an output member of the transmission. The actual output torque operating on the output member ultimately powers a set of drive wheels to propel the vehicle. Shift times in such transmissions can be relatively lengthy. Additionally, the output torque capacity or capability in a vehicle having an EV powertrain may suddenly and perceptibly increase, for example when available battery power suddenly increases.